1. Field of the Invention
The invention relates to a control device for the internal combustion engine and the automatic gearbox of a motor vehicle, including a tempomat and an input device with operating elements which permit commands to be input to the gearbox controller in the gearbox mode of the input device.
2. Description of the Prior Art
A control device of the type mentioned at the beginning is disclosed in DE 691 00 712 T2. The control device is located in a motor vehicle which has an internal combustion engine and an automatic gearbox coupled to the internal combustion engine. In this case, the automatic gearbox is actuated by the control device in a known way, that is to say it is switched over between various transmission ratios as a function of operating parameters of the motor vehicle. In particular, the switchover between two gears takes place in accordance with prescribed characteristics as a function of the engine speed and the fuel feed to the engine.
Furthermore, the known control device includes an input device in the form of a shift lever for the driver to input operating commands. In this case, the input device is always in a xe2x80x9cgearbox modexe2x80x9d in which the set positions of the shift lever are interpreted as commands for the gearbox controller. In particular, the shift lever can be used to set the operating states of xe2x80x9cforward drivingxe2x80x9d (D), xe2x80x9cneutral positionxe2x80x9d or xe2x80x9cidlingxe2x80x9d (N), and xe2x80x9crearward drivingxe2x80x9d (R).
Furthermore, the control device of DE 691 00 712 T2 has what is termed a tempomat, that is to say a device for automatically regulating the cruising speed (xe2x80x9ccruise controlxe2x80x9d). A desired cruising speed can be prescribed via such a tempomat and is then automatically maintained by the vehicle without the driver needing to perform further operations. However, the driver retains the option of overriding the prescriptions of the tempomat by actuating the gas pedal or the brake, and thus of being able to intervene at any time in the driving process.
With the tempomat switched in, the control device disclosed in DE 691 00 712 T2 acquires specific vehicle operating parameters and their change with time, in order to detect whether the vehicle is subject to increased power requirements when driving uphill. In this case, the control device for the automatic gearbox is switched over into what is termed the xe2x80x9ckick-downxe2x80x9d operating state which can normally (with disconnected tempomat) be switched in only by the driver by kicking the gas pedal down completely. In this kick-down operating state, the engine speeds prescribed for a gear shift are raised (incremented) to increase power, and so the engine is driven at higher speed overall.
In the known control devices, the corresponding control modules for the automatic gearbox and for the tempomat are separated from one another and are to be actuated via dedicated operating elements in each case. This leads to a higher number of operating elements which are to be actuated by the driver, and thus to a greater complexity in the vehicle control, an increased space requirement in the instrumented area of the vehicle and, not least, to higher manufacturing costs for the vehicle.
Against this background, it was the object of the present invention to configure a control device of the type mentioned at the beginning in a fashion which is more cost-effective, compact and simpler to operate.
The control device serves for controlling the internal combustion engine and the automatic gearbox, coupled thereto, in a motor vehicle. It contains a tempomat, that is to say an automatic cruise control, and an input device with operating elements which, in the xe2x80x9cgearbox modexe2x80x9d of the input device, permit setting of the gearbox controller or inputting of commands for this purpose. The control device is defined by the fact that its input device can adopt a tempomat mode in which at least one of the operating elements permits setting of the tempomat or inputting of commands for this purpose.
By contrast with known control devices, the control device according to the invention is therefore not split into two separate and mutually independent modules, one module exclusively serving the purpose of gearbox control, and the other module exclusively serving the purpose of speed control (tempomat). Rather, the two control tasks are combined, at least with reference to the input device, which constitutes the user interface of the control device. This comes about by virtue of the fact that, in addition to the gearbox mode, the input device can also further adopt a second operating mode, the xe2x80x9ctempomat modexe2x80x9d, in which the actuation of at least one of the operating elements is no longer interpreted as a command for the gearbox controller, but as a command for the tempomat. The double-function operating element can be used, for example, to switch in or disconnect the activity of the tempomat, or to prescribe the desired speed.
Owing to this double function of at least one operating element and of the input device, it is possible, firstly, to achieve a simplification of the handling of the control device, since the number of operating elements is diminished, and thus the risk of maloperations is reduced. In particular, in the case of input devices arranged on a steering wheel, such a minimization of the number of operating elements is particularly to be desired. Secondly, savings in space and components are also achieved, the latter leading, in turn, to lower manufacturing costs for the control device.
In accordance with one embodiment of the control device, among the operating elements is an input element which is denoted below in a simplified way as a xe2x80x9cswitchxe2x80x9d and which serves to set the xe2x80x9cforward drivingxe2x80x9d operating state for the gearbox controller. In the operating state of forward driving, the forward gears of the gearbox are automatically changed in a known way depending on the operating conditions of the vehicle. Furthermore, the input device is set up such that it can be switched back and forth between the gearbox mode in the xe2x80x9cforward drivingxe2x80x9d operating state and the tempomat mode by actuating the switch for forward driving. The switch for forward driving therefore acquires the additional function of switching the input device over between said modes. A separate switch for switching over between the gearbox and tempomat modes can therefore be saved by means of the additional function of this switch. Furthermore, the forward driving switch is suggested, in particular, because the tempomat mode is always required only in the xe2x80x9cforward drivingxe2x80x9d operating state of the gearbox controller, and the switch for forward driving usually has no function in the tempomat mode. This switch is required only for the purpose of switching over from other operating states such as, for example, the neutral position or rearward driving into the forward driving operating state.
In accordance with another advantageous refinement of the invention, among the operating elements of the input device are input means for setting variables, the actuation of which in the gearbox mode of the input device effects a gear shift, and in the tempomat mode of the input device effects a change in the desired speed. The input means for setting variables can be used to set the value of a variable which can change in steps or continuously. In the gearbox mode, this variable is, in particular, the (discrete) stage of the selected gear, that is to say the value 1, 2, 3, etc. By contrast, in the tempomat mode the variable is the desired speed which is to be maintained by the tempomat.
The input means for setting variables can, in particular, be two control switches, one control switch serving to increment the basic variable, and the other control switch serving to decrement it. Thus, in the gearbox mode the incrementing control switch can shift up by a gear stage, and in the tempomat mode it can raise the desired speed by a prescribed difference or a prescribed percentage. Correspondingly, in the gearbox mode the decrementing control switch can shift down by a gear stage, and in the tempomat mode it can lower the desired speed by a prescribed difference or a prescribed percentage.
Furthermore, the input device is preferably configured such that it goes over from the tempomat mode into the gearbox mode upon actuation of the motor vehicle brake if it was in the tempomat mode initially. This refinement takes into account that after actuation of the brake there is a higher probability that the driver wishes to use the input device to operate the gearbox controller. For example, after a stoppage of the motor vehicle the driver will regularly want to bring the gearbox controller into the operating state of the neutral position.
The input device is preferably configured in this case in such a way that the outlined automatic transition from the tempomat mode to the gearbox mode upon actuation of the brake constitutes a setting of the configuration of the control device which the driver can optionally switch in or disconnect. In a similar way, actuation of the gas pedal can effect a transition from the tempomat mode to the gearbox mode. This automatic transition can also preferably be designed as a configuration of the control device which can be selected by the driver.
It may be pointed out that the transition from the tempomat mode to the gearbox mode of the input device (or vice versa) is not to be equated with the termination (starting) of the activity of the tempomat. Rather, as is known from the prior art, the driver can, if required, override the automatic control of the tempomat by actuating the brake and/or the gas pedal, control going over to the tempomat again when this overriding is withdrawn.
The operating elements of the input device can include, in particular, a switch for rearward driving and a switch for the neutral position of the gearbox. In this case, the input device is preferably configured such that the actuation of the switch for rearward driving has no effect in the tempomat mode. Alternatively, however, it is also possible, for example, for the activity of the tempomat to be switched in or disconnected via this switch. The actuation of the switch for the neutral position can have the same function in the tempomat mode as in the gearbox mode, that is to say can effect the transition of the gearbox to idling.
In accordance with one development, the control device includes a display device on which an indication of the tempomat mode is displayed when the input device is in the tempomat mode. Thus, with the aid of the display device the driver has the information at any time on whether the input device is in the tempomat mode or not (that is to say in the gearbox mode).